Background: The primary objective of the study was to evaluate the effect of nitoglycerine (NTG) and sodium nitroprusside (SNP) on serum lactate (S. lactate), mixed venous oxygen saturation (SvO2), and mixed venous arterial carbon dioxide difference (V-ACO2) during cardiopulmonary bypass (CPB). The secondary objectives included the effect on mortality, end organ dysfunction, requirement of vasopressors, duration of mechanical ventilation (MV), intensive care unit (ICU) stay and hospital stay.
Materials and Methods: A prospective randomized single blinded study was conducted in 40 patients aged between 20 years and 70 years who underwent cardiac surgery on CPB. The patients were randomly divided into Group N (n = 20) receiving NTG (0.5–2 mic/kg/min) and group S (n = 20) receiving SNP (0.5–2 mic/kg/min) from the commencement of total CPB up to complete rewarming (nasopharyngeal temperature >36.5°C). Arterial blood gases and S. lactate were measured at baseline, after institution of total bypass, after completion of cooling and rewarming, at weaning off CPB and admission to ICU. Venous blood gas (VBG) was sampled from the venous reservoir immediately after institution of total bypass and completion of rewarming. Urine output, dose of rescue vasodilator, use of inotropes and vasopressor after CPB, end organ dysfunction, duration of MV, ICU, and hospital stay were noted.
Results: Though the SvO2at the end of CPB decreased significantly from the baseline (P < 0.05), it was similar between the groups. There was no difference in V-ACO2too. The S. lactate markedly increased (P = 0.00) from the baseline; however, only the S. lactate at admission to ICU was significantly lower in Group S (P = 0.034). There was no difference in mortality, end organ dysfunction, requirement of vasopressors, duration of MV, ICU, and hospital stay.
Conclusion: The authors showed that S. lactate increased with CPB and this increase did not correlate with SvO2and V-ACO2. NTG and SNP were comparable in their effect on indices of tissue perfusion.